The correct order of ionisation energy of C, N, O and F is

Options

A. `F lt N lt lt C lt O `
B. `C lt N lt O lt N`
C. `C lt O lt N lt F`
D. `F lt O lt N lt C`

Answer

C

Explanation

Along a period `Delta_(i)H_(1)` increases from left to right (i.e., from C to F ) due to decreasing atomic size and increasing effective nuclear charge . But due to more stable exactly half- filled electronic configuration N has higher `Delta_(i)H_(1)` than that of O Thus , the overall increases in the order :
`C lt O lt N lt F` i.e., option ( c) is correct